Refrigeration system

ABSTRACT

The present invention is directed to refrigeration systems of the type referred to in the art as heat pumps comprising a compressor, a pair of series-connected heat exchangers, reversing valve means for reversibly connecting the compressor to the heat exchangers for effecting flow of refrigerant through a portion of the circuit in either direction, refrigerant flow control means in the circuit, and a refrigerant container or receiver connected between the two heat exchangers for storing a portion of the refrigerant charge during operation of the system, the container being so constructed and arranged as to readily accommodate varying charge imbalances in the system and also having in communication therewith tubular means for effecting essentially complete removal of oil entrapped in the container and its return to the compressor when the system is reversed from the heating to the cooling cycle, thereby assuring an adequate supply of oil in the compressor for lubrication purposes.

United States Patent [72] lnventor Harry T. Hale Bridgeport, NY. [21] Appl. No. 812,215 [22] Filed Apr. 1, 1969 [45] Patented May 25, 1971 [73] Assignee Carrier Corporation Syracuse, N.Y.

[54] REFRIGERATION SYSTEM 2 Claims, 1 Drawing Fig.

[52] US. Cl 62/149, 62/160, 62/174, 62/192, 62/470 [51] Int. Cl F25b 45/00 [50] Field of Search 62/ 149, 160, 174,192,470

[56] References Cited UNITED STATES PATENTS 3,006,155 10/1961 Vanderlee 62/149 3,074,249 1/1963 Henderson 62/149 3,163,016 12/1964 Kennedy 62/149 3,212,284 10/1965 Henderson 62/149 3,264,838 8/1966 Johnson 3,324,671 6/1967 Hamish Primary ExaminerWilliam J. Wye AttorneysI-1arry G. Martin, Jr. and J. Raymond Curtin and arranged as to readily accommodate varying charge imbalances in the system and also having in communication therewith tubular means for efiecting essentially complete removal of oil entrapped in the container and its return to the compressor when the system is reversed from the heating to the cooling cycle, thereby assuring an adequate supply of oil in the compressor for lubrication purposes.

Patented May 25, 1971 INVENTOR.

HARRY T. HALE. m is 9 ATTORNEY.

REFRIGERATION SYSTEM BACKGROUND OF THE lNVENTlON Conventionally, a heat pump is provided with reversing means for directing the flow of high-pressure refrigerant gas from a compressor into either of two series-connected heat exchangers and for returning the low-pressure refrigerant from the other heat exchanger to the compressor. The conditions prevailing during operation of the system in one direction as compared to those which exist while operating in the other direction are usually such as to require, for the most optimum performance of the heat pump, that the refrigerant charge flowing through the system be less in one direction than when operating in the other direction. In most heat pumps, it is desirable to decrease the effective refrigerant charge flowing in the circuit during the winter or heating cycle operation over the charge designed to give optimum performance during the summer or cooling operation.

A well-known arrangement for automatically taking care of the different refrigerant flow requirements of the system is to utilize a receiver in which there is stored a portion of the refrigerant charge during operation of the system on the heating cycle. Various receiver configurations have been employed for this purpose, and an exemplary structure'takes the form of a deal-en d" receptacle which houses therein a standpipe normally provided with an orifice adjacent its lower end for facilitating return to the compressor of oil trapped in the receptacle through conduit means connected atone end to the standpipe lower end.

While a receiver of the character just briefly described has proven its effectiveness for most applications, a need exists for a receiver so constructed and arranged in the refrigeration system as to more readily accommodate refrigerant charge imbalance variations in the system and when employed in combination with a relatively slender communicating oil return tube, the receiver is essentially completely emptied of the oil which was trapped therein.

SUMMARY OF THE INVENTION The present invention is particularly directed to a refrigeration system or heat pump which incorporates therein a refrigerant tank or receiver located in a closed reversible refrigerant circuit between indoor and outdoor heat exchangers, the tank being connected at one end to one of the heat exchangers for receiving during the heating cycle condensed liquid refrigerant therefrom and simultaneously storing within the tank or receiver a portion of the liquid refrigerant while the remainder thereof is passed through the opposite end of the receiver to the other heat exchanger to be evaporated therein. Oil from the compressor naturally is entrapped in the receiver, and when the heat pump is reversed from the heating to the cooling-cycle, the stored liquid refrigerant boils off, passes from the top or one end of the receiver to the heat exchanger which supplied the stored liquid, and by provision in accordance with this invention of a relatively slender tube or capillary connecting the lower end of the receiver to the last-mentioned heat exchanger, the trapped oil completely and rapidly drains from the receiver and is returned to the compressor.

By this invention, as will be pointed out in detail hereinafter, the described receiver possesses considerable versatility in that it can accommodate significant variations in the refrigerant charge imbalance in the system as may be occasioned by different component combinations, and the oil return device when constructed and positioned as described assures rapid and complete drainage of the receiver.

BRIEF DESCRIPTION OF THE DRAWING The single view is a diagrammatic illustration of a reverse cycle refrigeration system of the split-unit type embodying the novel concepts of the present invention.

DESCRlPTlON OF THE PREFERRED EMBODIMENT Referring now to the drawing, there is shown a heat pump comprising a split refrigeration system which includes an indoor unit 10 and an outdoor unit 12 adapted to be connected in the field during installation of the heat pump by means of refrigerant lines or conduits l4 and 16, the lengths of which will obviously depend upon the distance between the two units in any particular installation, and therefore, the total volume of thesystem cannot be determined until after the installation is made. The line 16 comprises part of a relatively longer conduit generally indicated by the reference numeral 18 for connecting an indoor heat exchanger 20 forming part of the indoor unit 10 with an outdoor heat exchanger 22 forming a part of the outdoor unit 12.

The conduit 18 also includes flow control or flow-restricting means for maintaining the pressure difference between the indoor heat exchanger 20 and the outdoor heat exchanger 22. In the embodiment of the invention shown, the indoor unit 10 includes flow control means taking the form of a thermal expansion valve 24 and a bypass line including a check valve 26 which bypasses refrigerant around the thermal expansion valve 24 when the heat pump is operated as a heating unit and the indoor heat exchanger 20 is functioning as a condenser. The outdoor unit 12 comprises flow control means desirably in the form of a thermal expansion valve 28 and a bypass line including a check valve 30 which bypasses refrigerant around valve 28 when the heat pump is operating on the cooling cycle in which the outdoor heat exchanger 22 functions as a condenser.

A compressor 32 having an inlet 34 connected to a suction line 36 and an outlet 38 connected to a discharge line 40 and a reversing valve 42 connected to the suction and discharge lines provide means for effecting flow of refrigerant through the refrigerant circuit including the two heat exchangers in either direction, whereby the indoor unit 10 may be operated either as a heating unit in which the indoor heat exchanger 20 functionsas a condenser, or as a'cooling unit in which the indoor heat exchanger 20 functions as an evaporator. The compressor 32 and reversing valve 42 may be supplied as a separate unit or may be part of either of the units 10 and 12. in the illustrated embodiment of the invention they form part of the outdoor unit 12 in which case the reversing valve 42 is connected to the outdoor heat exchanger 22 by means of a conduit 44 and to the indoor heat exchanger 20 by means of conduits 46, 14 and 48.

As also appears in the drawing, the conduit 48 has connected thereto header means 50 which connect with the indoor heat exchanger 20, the opposite end of this same heat exchanger being in communication with distributor means 52. Header means 54 and 56 are also provided in connecting relation with opposite ends of the outdoor heat exchanger 22.

For optimum operation of a heat pump of this type comprising flow control means for controlling the pressure differential between the two heat exchangers, a smaller circulating charge is desired on the heating cycle than on the cooling cycle. To provide a decrease in the effective refrigerant charge when the heat pump is changed over from operation on the cooling cycle to the heating cycle, and an increase in the effective refrigerant charge when the refrigeration system is reversed from heating to cooling, there is provided a storage tank or receiver 58 between the indoor heat exchanger 20 and the flow-restricting'means. The container or receiver is connected at one end which is the upper end thereof, to the distributor means or like device '52 by a conduit 60 'and at its opposite or lower end to the conduit 18 by means of conduit 62. Also communicating with the-lower end of the receiver 58 is oil return means 64 which preferably takes the form of a relatively small diameter tube or capillary connected to the distributor 52 through the conduit 60 for returning oil to the compressor 32 when the heat pump is changed over from the heating to the cooling cycle and the indoor heat exchanger is functioning as an evaporator. Additionally, the capillary tube 64 performs the important function of minimizing liquid flow when the system is on the heating cycle, thus forcing the liquid through the receiver. While not shown, there may be provided in the conduit 62 a trap of inverted generally U-shape configuration to prevent the accumulation of oil in the conduit 62 from its point of connection to the lower end of the receiver 58 down to the check valve 26 when the heat pump is on the cooling cycle and the valve 26 is closed.

In contrast to known receivers, generally termed as deadend" receptacles, and which house therein a standpipe open at its upper end and provided adjacent its lower end with an oil discharge orifice for returning trapped oil to the compressor, the receiver of this invention and oil return capillary, when constructed and arranged as shown, have several advantages. First, since the receiver shown is of variable capacity, it possesses considerable versatility in that it can be employed without substantial structural changes thereto for a wide variety of component combinations. For example, under a particular set of environmental conditions, the size of the indoor and outdoor heat exchangers, and more specifically the internal volume thereof, are preselected so that when the system is charged and operating, a particular volume of excess refrigerant will be stored in the receiver when the heat pump is on the heating cycle. lllustratively, and depending in part on he particular refrigerant employed, the optimum charge for the system may be pounds when the heat pump is on the cooling cycle and 8 pounds when on the heating cycle, leaving an excess of 2 pounds of refrigerant to be stored in the receiver during the latter cycle. However, under a different set of conditions, as in a geographical area where the winters are relatively severe and the summers mild, a lesser volume of excess refrigerant would be stored or it may even be desirable to locate the receiver and oil return capillary on the line leading to the outdoor heat exchanger in relatively close proximity thereto and to store refrigerant during the cooling cycle. In any event, and particularly when the heat pump is being operated as shown in the drawing, refrigerant imbalances in he system from any one of a number of causes can be readily accommodated.

Second, and as was pointed out earlier, the provision of a relatively slender tube or capillary as the oil return means, when located as shown, assures rapid and complete drainage of oil from the receiver when the heat pump cycle is reversed from heating to cooling.

The operation of the refrigeration system of this invention will now be described. On the cooling cycle, hot compressed refrigerant gas is discharged from the compressor 32 through the discharge conduit 40 to the reversing valve 42 which directs it through the conduit 44 and the header 54 into the outdoor heat exchanger 22 wherein the refrigerant is condensed and flows to the header 56. It is to be noted at this point that the thermal expansion valve 28 is connected by a capillary to sensing means 66 on the conduit 44, the capillary transferring the pressure in the sensing means or bulb 66 to the valve. Condensed refrigerant from the outdoor heat exchanger 22 and header 56 bypasses valve 28 and flows through the check valve 30 which is open by reason of the presence of essentially balanced high-pressure liquid on opposite sides thereof. The refrigerant accordingly takes the path of least resistance. The condensed refrigerant then passes through the conduit 16 forming a part of the line 18 and through the valve 24.

During operation of the heat pump on the cooling cycle, a pressure differential exists on opposite sides of the check valve 26 as between high-pressure liquid refrigerant from the conduit l6 and low-pressure refrigerant gas acting upon the opposite side of the check valve. This discourages flow of refrigerant from the receiver 58 through check valve 26. Highpressure liquid bypasses the check valve 26, as noted, moves through the valve 24 which is connected to sensing means 68 in the manner of valve 28 and the bulb 66, and from the distributor means or like device 52 into the indoor heat exchanger 20 in which the refrigerant is evaporated by absorbing heat from the surrounding atmosphere, whereby the air in the dwelling or other structure being conditioned by the heat pump is cooled. Gaseous refrigerant from the heat exchanger 20 is withdrawn at relatively low temperature and pressure and passes through the conduits 48, 14, and 46, the reversing valve 42 and suction conduit 36 into the compressor 32.

When the reversing valve 42 is reversed by hand-manipula ble means (not shown) or a similar device for operation of the refrigeration system on the heating cycle, hot compressed refrigerant gas from the compressor 32 is discharged through the discharge conduit 40 to the reversing valve 42 which directs it through the connecting conduits 46, 14, and 48 to the header 50 communicating with the indoor heat exchanger 20 functioning on the heating cycle as a condenser. The hot refrigerant gives up its heat of condensation to the space being conditioned, and the condensed or liquid refrigerant fiows through the distributor means 52 and conduit 60 into the receiver 58 wherein a portion thereof collects, the volume of this portion depending generally upon the refrigerant charge imbalance in the system as controlled by the particular component combination selected to meet the environmental needs.

The volume of liquid so collected in the receiver 58 represents the difference between the optimum charges on the heating and cooling cycles, and as was previously noted, the collected liquid has trapped therewith oil which has passed to the heat exchanger 20 from the compressor 32. The condensed liquid not collected, which constitutes the optimum charge for efficient operation on the heating cycle, passes through the conduit 62. Since the check valve 26 is subjected on opposite sides thereof to relatively high-pressure liquid refrigerant and is thereby open, valve 24 is bypassed and highpressure liquid refrigerant, with some oil entrained therewith, passes through the conduit 16. The check valve 30 is closed at this time by reason of high-pressure liquid acting upon one side and low-pressure gas on the other, the refrigerant thereby bypasses the valve 30, and flows through valve 28 and moves therefrom as a liquid-gas mixture into the outdoor heat exchanger 22 extracting heat from the outdoor air. The lowtemperature low-pressure gas then passes through the reversing valve 42 and suction line 36 to the compressor 32.

Upon reversal of the heat pump from the heating to the cooling cycle, liquid refrigerant which has condensed in the receiver and been collected therein during the heating cycle evaporates or boils off when the system is changed over to the cooling cycle and passes as vapor from the upper end of the receiver 58, through the conduit 60 and into the distributor 52 where it combines with refrigerant passing through valve 24 from the conduit 16 into which it flowed from the outdoor heat exchanger 22. It is to be noted at this point that the refrigerant evaporating in the receiver is added slowly to the system, thereby reducing floodback on changeover. Generally simultaneous with evaporation of the excess refrigerant in the receiver 58, the oil trapped therein flows from the bottom of the receiver 58, as the boiling refrigerant entrains same flows through the oil return capillary 64 to the distributor 52, and is returned to the compressor 32 entrained with refrigerant leaving the indoor heat exchanger 20 and moving through conduits 48, 14, and 46 to reversing valve 42.

It will be appreciated that capillary tubes may be substituted for the thermal expansion valves shown and that the combination of a receiver and oil return means may be in close association with the outdoor heat exchanger rather than in the location appearing in the drawing. These and other modifications may of course be effected without departing from the spirit of the invention or the scope of the subjoined claims.

lclaim:

l. A heat pump comprising a refrigeration system including a first heat exchanger, a second heat exchanger series connected to the first heat exchanger, means including a compressor having an inlet and outlet, and reversing valve means for reversibly connecting said compressor to said heat exchangers for effecting flow of refrigerant through said heat exchangers in either direction whereby said heat pump may be operated on a cooling cycle with said first heat exchanger functioning as an evaporator or on a heating cycle with said second heat exchanger functioning as an evaporator, first expansion means for regulating supply of refrigerant to the first heat exchanger, second expansion means for regulating supply of refrigerant to the second heat exchanger, a bypass conduit about said first expansion means, a check valve in said bypass permitting refrigerant flow therethrough when the heat pump is operating on a heating cycle, and preventing refrigerant flow therethrough when the heat pump is operating on a cooling cycle, a container connected in said bypass, said container receiving a portion of said total charge when said heat pump is operated on the heating cycle and discharging said portion into said circuit when said heat pump is operated on the cooling cycle, refrigerant passing through said bypass and said container to said second heat exchanger when the heat pump is operating on a heating cycle, and a capillary tube forming a part of and connecting portions of said bypass on opposite sides of said container and communicating with said first heat exchanger and with said container for returning to said compressor when said heat pump is reversed from the heating to the cooling cycle any oil which is trapped insaid container with said portion of said total refrigerant charge when said 

1. A heat pump comprising a refrigeration system including a first heat exchanger, a second heat exchanger series connected to the first heat exchanger, means including a compressor having an inlet and outlet, and reversing valve means for reversibly connecting said compressor to said heat exchangers for effecting flow of refrigerant through said heat exchangers in either direction whereby said heat pump may be operated on a cooling cycle with said first heat exchanger functioning as an evaporator or on a heating cycle with said second heat exchanger functioning as an evaporator, first expansion means for regulating supply of refrigerant to the first heat exchanger, second expansion means for regulating supply of refrigerant to the second heat exchanger, a bypass conduit about said first expansion means, a check valve in said bypass permitting refrigerant flow therethrough when the heat pump is operating on a heating cycle, and preventing refrigerant flow therethrough when the heat pump is operating on a cooling cycle, a container connected in said bypass, said container receiving a portion of said total charge when said heat pump is operated on the heating cycle and discharging said portion into said circuit when said heat pump is operated on the cooling cycle, refrigerant passing through said bypass and said container to said second heat exchanger when the heat pump is operating on a heating cycle, and a capillary tube forming a part of and connecting portions of said bypass on opposite sides of said container and communicating with said first heat exchanger and with said container for returning to said compressor when said heat pump is reversed from the heating to the cooling cycle any oil which is trapped in said container with said portion of said total refrigerant charge when said heat pump is operated on the heating cycle.
 2. A heat pump according to claim 1 in which the refrigeration system includes a second bypass conduit about said second expansion means and a check valve in said second bypass conduit permitting refrigerant flow therethrough when the heat pump is operating on a cooling cycle and preventing refrigerant flow therethrough when the heat pump is operating on a heating cycle. 